In this composition, the lake surface only covers 6%-8% of the composition. Yet the lake is a dominant feature of the composition due to the converging lines that lead the viewer's eye to the center of the painting before crossing to the other side.
I commuted to Santa Rosa from East Bay in Northern California for several years. I'd often take the rural Petaluma route through farm country. The soft texture of pastel gives this sketch an indication of red barns passed by quickly on the roadside.